textproduct: Albany

WHAT HAS CHANGED

Confidence increasing for moderate to heavy snowfall across portions of the southeast Catskills/mid Hudson Valley late Friday through Saturday morning, with light/moderate amounts possible farther north and east. Winter Storm Watch issued for Ulster County for late Friday afternoon through early Saturday afternoon.

KEY MESSAGES

1. Accumulating snow expected late Friday afternoon into Saturday morning, with the most impactful snowfall mainly near and south of I-90.

2. Precipitation develops Sunday afternoon and may continue into Monday morning, likely beginning as snow or a wintry mix (including freezing rain) before potentially ending as plain rain.

DISCUSSION

KEY MESSAGE 1...

Arctic cold front swings through late tonight into Christmas morning, possibly accompanied by scattered snow showers/flurries with gusty northwest winds developing in its wake Christmas afternoon, with some gusts of 30-40 mph possible. A wave of low pressure will develop along this boundary across the Great Lakes region and track east-southeast Friday into Saturday. A swath of of light to moderate snow will be likely to the north/northeast of the low's track, along with the possibility of a narrow band of heavy snow due to strong isentropic ascent along with embedded frontogenetical forcing.

Latest 24-hr NBM probs for > 2" of snowfall through 7 AM Saturday are 60-90% and for > 4" are 50- 80% from the I-90 corridor south. Probs for > 6" are 40-60% limited to the E. Catskills and western portions of mid Hudson Valley, maximized across Ulster County. Based on this increased confidence and in collaboration with surrounding offices and WPC, we have issued a Winter Storm Watch for Ulster County for 4 PM Friday through 1 PM Saturday, where confidence for around/slightly greater than 7" exists. Light to moderate amounts are expected farther north and east to the I-90 corridor, with lighter amounts farther north.

We expect a sharp northern gradient to snowfall amounts with this system, given expectation of very dry low level air draining south and west from arctic high pressure anchored across eastern Canada amid strong zone of mid/upper level confluence and associated subsidence. A slight deviation in storm track will result in significant changes in expected snowfall amounts.

Although the steadiest snowfall is expected Friday night through mid morning Saturday, periods of light snow may persist through much of Saturday, and could expand northward to include the southern Adirondacks and southern VT as low level moisture eventually builds northward.

Very cold temperatures are expected before and during the anticipated snowfall, mainly in the single digits and teens Friday/Friday night before slowly climbing into the 20s by late Saturday. Thus, even where snowfall remains light in intensity, very cold ground surfaces may make snow removal more difficult and could result in very slippery roads across the region Friday night into most of Saturday.

KEY MESSAGE 2...

Next system approaches from the west for late Sunday into Sunday night. This system looks to have warmer air aloft moving into the region, however shallow cold air is likely to persist into Sunday night. This scenario favors a wintry mix, primarily as freezing rain and sleet, perhaps mixed with some snow at the start especially for areas north and east of Albany. Enough low level warming may allow for precipitation to change to plain rain later Sunday night, especially for areas from Albany and points south and east.

13Z/NBM 24-hour probs ending 7 AM Monday for >0.01" of freezing rain are 40-80% across the SW Adirondacks, upper Hudson Valley and Saratoga region, as well as across higher elevations in southern VT, and generally 20-50% elsewhere, highest across the eastern Mohawk Valley and higher terrain of the Berkshires, Litchfield Hills and eastern Catskills. Similar probs for >0.10" of freezing rain are generally 10-30% across the SW Adirondacks and higher terrain of southern VT/eastern Catskills. However, NBM might be a bit too warm and may scour out low level cold air too quickly, especially for embedded valley regions north of I-90, so will need to watch future trends for potential ice accumulations. At the very least, very cold ground surface temperatures may create treacherous travel conditions late Sunday afternoon into Sunday night as the precipitation begins.

In the wake of this system, colder temperatures and gusty winds will overspread the region early next week, along with some lake effect snow showers/squalls for areas primarily north/west of Albany.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Through 00z Friday...Passing high pressure will keep VFR conditions in place through early tonight, with light north winds around 5-10 kts becoming light & variable. An arctic cold front will move through the region late tonight into Thursday morning, resulting in winds increasing out of the northwest with gusts around 20-25 kts by midday. These winds will persist through the remainder of the period. Ceilings will remain primarily VFR with the exception of KPSF, where scattered high-end MVFR ceilings will be possible for a brief period late Thursday morning before retuning to VFR levels for the remainder of the period.

Thursday Night: Moderate Operational Impact. Breezy. NO SIG WX. Friday: Low Operational Impact. Slight Chance of SN. Friday Night: High Operational Impact. Likely SN. Saturday: Moderate Operational Impact. Chance of SN. Saturday Night: No Operational Impact. NO SIG WX. Sunday: Moderate Operational Impact. Chance of RA...FZRA. Sunday Night: High Operational Impact. Definite RA...FZRA. Monday: High Operational Impact. Breezy. Likely RA...SN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Storm Watch from Friday afternoon through Saturday afternoon for NYZ063-064. MA...None. VT...None.